On Mon, Sep 12, 2016 at 9:25 PM, Tom Herbert <t...@herbertland.com> wrote:
> On Mon, Sep 12, 2016 at 8:00 PM, Alexander Duyck
> <alexander.du...@gmail.com> wrote:
>> On Mon, Sep 12, 2016 at 3:13 PM, John Fastabend
>> <john.fastab...@gmail.com> wrote:
>>> The BQL API does not reference the sk_buff nor does the driver need to
>>> reference the sk_buff to calculate the length of a transmitted frame.
>>> This patch removes an sk_buff reference from the xmit irq path and
>>> also allows packets sent from XDP to use BQL.
>>>
>>> Signed-off-by: John Fastabend <john.r.fastab...@intel.com>
>>> ---
>>> drivers/net/ethernet/intel/e1000/e1000_main.c | 7 ++-----
>>> 1 file changed, 2 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c
>>> b/drivers/net/ethernet/intel/e1000/e1000_main.c
>>> index f42129d..62a7f8d 100644
>>> --- a/drivers/net/ethernet/intel/e1000/e1000_main.c
>>> +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
>>> @@ -3882,11 +3882,8 @@ static bool e1000_clean_tx_irq(struct e1000_adapter
>>> *adapter,
>>> if (cleaned) {
>>> total_tx_packets += buffer_info->segs;
>>> total_tx_bytes += buffer_info->bytecount;
>>> - if (buffer_info->skb) {
>>> - bytes_compl +=
>>> buffer_info->skb->len;
>>> - pkts_compl++;
>>> - }
>>> -
>>> + bytes_compl += buffer_info->length;
>>> + pkts_compl++;
>>> }
>>> e1000_unmap_and_free_tx_resource(adapter,
>>> buffer_info);
>>> tx_desc->upper.data = 0;
>>
>> Actually it might be worth looking into why we have two different
>> stats for tracking bytecount and segs. From what I can tell the
>> pkts_compl value is never actually used. The function doesn't even
>> use the value so it is just wasted cycles. And as far as the bytes go
>
> Transmit flow steering which I posted and is pending on some testing
> uses the pkt count BQL to track inflight packets.
>
>> the accounting would be more accurate if you were to use bytecount
>> instead of buffer_info->skb->len. You would just need to update the
>> xmit function to use that on the other side so that they match.
Okay, that makes sense.
But as I was saying we might be better off using the segs and
bytecount values instead of the skb->len in the xmit and cleanup paths
to get more accurate accounting for the total bytes/packets coming and
going from the interface. That way we can avoid any significant
change in behavior between TSO and GSO.
- Alex
